1. The Field of the Invention
The present disclosure relates generally to support devices used for subsurface materials, and more particularly, but not necessarily entirely, to devices, sometimes referred to as roof plates, for receiving roof bolts to assist in preventing roofs of underground mines from caving in.
2. Description of Related Art
It is common practice in the mining industry to support underground mine roofs with support members to prevent roof cave-ins. One method of supporting underground mine roofs includes attaching lower levels rock strata to upper layers of rock using roof bolts. Roof bolts may vary in length and diameter, but may typically be sized one-half inch or more in diameter and 30 inches to 12 feet or more in length. Other varieties of roof bolts, such as cable bolts, may be 10 to 24 feet in length, for example. The roof bolts may be formed as rigid members such as rebar or threaded rod bolts, or the roof bolts may be formed as multi-strand cable bolts. Holes may be drilled in the ceiling of a mine and the roof bolts may be inserted to tie the rock strata in the ceiling with upper layers of rock.
Some embodiments of roof bolts may also include use of epoxy or polyester resins and various types of cement. After a hole is placed in the mine ceiling, an epoxy or polyester resin in a pliable plastic tube may be inserted in the hole. Next, a roof bolt may be inserted in the hole which may tear the packaging for the epoxy or polyester resin and allow the resin to mix and spread to the surrounding rock layers. The resin may set up or harden within a matter of seconds to thereby seal the bolt to the rock layers. Cements are much slower in setting and are, therefore, used where setting time is not critical.
A support member, commonly referred to as a bearing plate or a roof bolt plate, may be placed on the mine ceiling and held in place by a head or nut on the roof bolt. In cases where a threaded nut is used, it is tightened to bring the roof bolt plate snugly against the mine ceiling. The plate thereby functions as a washer to prevent the roof bolt from being drawn into the bolt hole in the ceiling of the mine. The roof bolts may be spaced at specified intervals along the mine ceiling, such as every four feet, for example, to provide adequate support to the mine roof. Accordingly, cave-ins in the mine may be prevented and the mine may be safely accessed.
Despite the advantages of the known roof bolt plate systems, improvements are still being sought. For example, roof bolts are known to break, thereby causing a portion of the bolt to be ejected from the ceiling causing a safety hazard. Attempts have been made to prevent the roof bolts from shooting out of the ceiling and causing a safety hazard. For example, a wire mesh, such as a chain link material and/or a rubber matting material, may be place over the ceiling to hold the roof bolts in the ceiling in the event the roof bolts are broken. However, the cost of materials and labor required to install wire mesh and rubber matting may be high.
Also, when a roof bolt breaks, a replacement roof bolt will usually have to be installed in close proximity to the broken bolt. This may add to the cost and time required to stabilize a roof. Additionally, the number of locations suitable for the roof bolt plates may be limited. Moreover, the loads supportable by the known roof bolt plate systems may be limited such that the prior art roof bolt plates may not be suitable in some situations. For example, the known roof bolt plate systems may not be effective in supporting soft or plastic soils.
The prior art is thus characterized by several disadvantages that are addressed by the present disclosure. The present disclosure minimizes, and in some aspects eliminates, the above-mentioned failures, and other problems, by utilizing the methods and structural features described herein.
The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims.